S3 connection hangs when S3 Put request times out server side.

Hi google friends! Apologies for the trouble!! We found this interesting issue when using tensorstore!! Thanks for taking a look ## Summary When an S3 PUT request is timed out server-side, the TensorStore client can hang for ~30 minutes before retrying. During this window, S3 access logs show zero retries — the request appears to be "in flight" on the client but dead on the server. The receive of the request is confirmed by s3 access logs. The ~30-minute gap matches the default OS-level TCP keepalive + retransmission timeout, which is the only thing that eventually forces the stalled socket closed. ## Root Cause 2 layers of missing timeout configuration compound each other: **1. S3 driver issues requests with no timeouts (`s3_key_value_store.cc:764`)** ```cpp auto future = owner->transport_->IssueRequest( request, internal_http::IssueRequestOptions(value_)); // IssueRequestOptions only sets payload; request_timeout and connect_timeout // remain at their defaults of absl::ZeroDuration(). ``` 2. Zero duration → curl sets nothing (curl_transport.cc:198-205) if (options.request_timeout > absl::ZeroDuration()) { // never true handle_.SetOption(CURLOPT_TIMEOUT_MS, ...); } CURLOPT_TIMEOUT_MS is never set, so libcurl has no deadline on the transfer. ## Workaround Set environment variables before launching your process: export TENSORSTORE_CURL_LOW_SPEED_TIME_SECONDS=30 export TENSORSTORE_CURL_LOW_SPEED_LIMIT_BYTES=1 This enables the low-speed watchdog: if fewer than 1 byte/sec is transferred for 30 seconds, libcurl aborts the request and the retry logic takes over. ## Suggested fix * Expose request timeout and connect timeout to s3 query driver